1. Field of the Invention
The present invention relates to an epoxy-based coating resin composition which facilitates the transcription of the printed letters or photographs developed by sublimation dyes on printing paper to the surface of potteries, glasses, marbles, metals or woods only by thermal treatment and more particularly, to the epoxy-based coating resin composition with 1) long-term storage stability due to the use of a mixture, of diethanolamine and triethanolamine as a hardening accelerator, 2) good depth in the transfer printing, and 3) a releasing property which promotes easier separation of printing paper from its coated surface after transfer-printed.
2. Description of the Related Art
It has been generally known that an epoxy-based resin composition containing a hardening agent is effective to transcribe the printed letters or photographs developed by sublimation dyes on printing paper to a coating layer by thermal treatment[Ger. Pat. No. 2,424,949(1974)]. A mixture of acryl and melamine resin as a coating layer was used to transcribe the printed letters or photographs developed by sublimation dyes on printing paper to aluminum pipes. An epoxy resin was finally coated [Jap. Pat No. 119,006(1979)].
A coating layer was required to transcribe the printed letters or photographs developed by sublimation dyes on printing paper to the surfaces of potteries, glasses, marbles, metals or woods, etc. It provided a rapid decoration with printed letters, patterns or photographs to the surface of potteries, glasses, marbles, metals or woods only by thermal treatment. In order to get a good transfer printing, the printed letters or photographs developed by sublimation dyes on printing paper was used. Then, it is necessary to get uniform thickness of a coating layer to be transfer-printed.
The essential properties of coating resin compositions used in transcribing the printed letters or photographs developed by sublimation dyes on printing paper to the coated surface are required as follows:
1. It must provide a coating layer with good transparency, chemical and water resistance, and good adhesion between original surfaces and its coated ones, etc. PA1 2. It must provide both good flexibility to prevent the coating layer from cracking caused by thermal contraction when dried and the ability to restrain the transcribed letters or photographs from discoloring by ultraviolet lights or air. PA1 3. It must produce a coating layer with initial and durable adhesive strength in the condition that the printed letters or photographs developed by sublimation dyes on printing paper are deeply transfer-printed only by thermal treatment. PA1 4. It must promote easier separation of printing paper from the coated layer printing after the thermal treatment. PA1 5. It must provide long-term storage stability at room temperature on the condition that hardening agents are in a same vessel.
Most of epoxy resins existed in the coating resin composition for transfer printing are bisphenol- or phenol-formaldehyde resin with oxirane rings, wherein their epoxide equivalent weight(EEW) is in the range of 180-3300. If EEW in the epoxy resins is below 220, the viscosity of the resins in a liquid state shows in the range of 2-230 poise, while if EEW exceeds 220, most of the resins are in a solid state.
A coating resin composition used in the transfer printing contains some kinds of hardening agents for its curing, and the resin composition containing the agents is unstable even at room temperature. Nevertheless, it is always necessary to enhance the strength, flexibility and heat resistance of the coating layer. The agents used here are amines, acid anhydrides, imidazoles and ureaformaldehyde resins, etc.
Also, in order to control the thickness of the coating layer, various organic solvents as a diluent are used. The weight ratio of aliphatic component to aromatic one as well as the molecular weight distribution in the resin composition is adjusted to get the flexibility of coating layer.
Tertiary amines[J. Appl. Polym. Sci., 10, 1813 (1770)], esters of boric. acid[Polym. Eng. Sci., 16, 353 (1976)], lewis acids[US. Pat. No. 5,521,011(1996)], organometallic compounds[J. Polym. Sci. C., 23, 765 (1968)], organic acid metallic,: salts[J. Polym. Sci. A-1., 8, 593 (1970)] and imiidazoles[J. Appl. Polym. Sci., 11, 1009 (1967)] are used to promote a hardening reaction.